Power-driven aerial extension ladders



Dec. 20, 1960 R. o. BALOGH 2,965,192

POWER-DRIVEN AERIAL EXTENSION LADDERS Filed March 15, 1954 2 Sheets-Sheet 1 Dec. 20, 1960 R. o. BALOGH POWER-DRIVEN AERIAL EXTENSION LADDERS a Sheets-Shet 2 Filed March 15, 1954 INVENTOR.

ROY O. BALOGH United States Roy 0. Balogh, Clayton, Mo., assignor to McCabe- Powers Body Company, a corporation of Missouri Filed Mar. 15, 1954, Ser. No. 416,339

13 Claims. (Cl. 182-66) This invention relates in general to certain new and useful improvements in aerial ladders and, more particularly, to a power-driven aerial extension ladder.

It is common practice in the maintenance of public utility lines, light poles, and overhead equipment to utilize trucks which are equipped with aerial extension ladders adapted for rapid elevation so that a workman can ascend to the proper and convenient height for carrying out the replacement or repair work required. For maximum utility, it is necessary that such ladders be capable of adjustment to various heights with ease and without sacrificing stability or security. Heretofore, however, the application of powered driving means to an aerial extension ladder has resulted in extremely heavy cumbersome equipment which is relatively inefficient in terms of power consumption and wears out in an unduly short period of time. One of the principal sources of wear or damage sustained in the operation of aerial extension ladders results from the impact encountered at each end of the stroke, that is to say, as the ladder reaches fully extended or fully retracted positions. Furthermore, since the extension ladder section is ordinarily rather heavy and is usually extended or lowered when the main ladder section is in substantially upright position, power driving means must have the characteristic of being able to start and stop under substantially full load conditions, and this requirement has heretofore led to the utilization of mechanisms which are-comparatively inefiicient, relatively slow-moving, and difiicult to decelerate at the end of a predetermined path of movement.

It is, therefore, the primary object of the present invention to provide a power-actuated aerial extension ladder which is simple and efiicient and is constructed to provide a safe, secure standing-support on which the workman will feel secure when aloft.

It is another object of the present invention to provide an aerial extension ladder of the type stated which is adapted for elevation, retraction, and related movements in a smooth, speedy manner with compact, relatively inexpensive, eflicient powered driving means.

It is also an object of the present inveniton to provide an aerial extension ladder provided with power-driven operating means for moving the extension ladder section from fully extended and fully retracted positions in a highly eflicient, smoothly operating manner and being adapted for rapid, but relatively shock-free, deceleration as the ladder section approaches the ends of its path of movement.

With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawings (two sheets)- Figure 1 is a rear end elevational view of a truck equipped with an aerial extension ladder constructed in Figure 2 is a fragmentary sectional view taken along line 2-2 of Figure 1;

atent ice Figure 3 is a fragmentary side elevational view of the aerial extension ladder showing in detail the hydraulic power system constituting a part of the present invention;

Figures 4, 5, and 6 are fragmentary sectional views taken along lines 44, 55, and 6-6, respectively, of Figure 3;

Figure 7 is a fragmentary sectional view taken along line 77 of Figure 5; and

Figure 8 is a schematic drawing showing the hydraulic circuit constituting a part of the present invention.

Referring now in more detail and by reference characters to the drawings, which illustrate a preferred embodiment of the present invention, A designates a conventional utility truck having a rearwardly extending floor 1. Rigidly mounted upon the floor 1 is a metal base plate 2 and welded upon the upper face thereof is a vertical tubular post 3 having closed-bottom hollow interior and being structurally stabilized by four angularly disposed brace bars 4. The base plate 2, post 3, and brace bars 4 are preferably welded together as an integral unit for convenient mounting upon any standard truck or vehicle. Furthermore, the hollower interior of the post 3 serves as a reservoir for oil or similar hydraulic fluid and is operatively associated with a conventional oil pump (not shown).

Rotatably swiveled upon the upper end of the post 3 is an external tubular post-sleeve 5 extending downwardly and concentrically around the post 3, terminating just above the upper end of the brace bars 4 and being internally provided with bearings, oil-transmission lines, and oil-distribution glands, more particularly described in my co-pending patent application, Serial No. 331,241, filed January 14, 1953, now Patent No. 2,777,737.

Welded upon the upper end of the post-sleeve 5, and extending symmetrically outwardly on opposite sides of the center line thereof, is a horizontal top plate 6, vertical apron plate 7, and back plate 8. Also welded to the top plate 6 and to the plates 7, 8, is a plurality of lateral plates 9 forming, in effect, a box-like head frame which is rigidly carried by the post-sleeve 5. The lateral plates 9 support axially aligned transversely extending pintles 10, and journaled thereon at its lower end is a main ladder section 11 consisting of two spaced parallel side rails 12, 13, having dielectric upper end portions 12', 13', respectively, the latter preferably being made of wood. The rails 12, 13, are provided with a plurality of uniformly spaced tubular rungs 14, the lowermost of which is mounted at its ends in clearance brackets 15, 16, and is internally provided with a rotatable shaft 17 operatively supported in bearings 18, 19, and being endwise rigidly connected to a reversible oil motor 20, which is of a type which develops a constant maximum torque at variable speed and which, furthermore, has the characteristic, when operating below such maximum, of developing .only that torque necessary to move the load. Such motors are commercially available and have been used for various purposes, but, so far as I am aware, have not been employed in connection with aerial ladders in combination with suitable controls to achieve the unique functions of the present invention.

Keyed or otherwise rigidly mounted upon the shaft 17 for operation within the clearance space aiforded by the brackets 15, 16, are pulleys 21, 22, drivingly connected to continuous or endless cables 23, 24;, respectively, which are, in turn, connected to an extension ladder section 25, as more fully described in a related patent application, Serial No. 416,088, filed contemporaneously herewith, and now Patent No. 2,933,150. The oil motor 20 is hydraulically connected to a hydraulic control system presently to be more fully described.

Mounted upon the outwardly presented face of the post-sleeve 5 is a conventional hydraulic control valve thetcase may be.

3 29 having two valve control levers 30, 31. Inasmuch as the interior mechanism of the hydraulic control valve 29 is substantially conventional, it is not shown or described in detail herein. It is suflicient merely to :point out that the control valve 29 is connected through a pressure supply line 32 and a return line '33, respectively, to the oil pump and the reservoir formed within the hollow interior of the post 3. One chamber c of the control valve 29, which is associated with the control lever 30, is similarly connected by a flexible oil pressure line 34 and a conventional hydraulic cylinder HCr -This particular chamber of the contro-l valve 29 is so arranged that when the valve control 30 is shifted; in one direction, oil pressure will be admittedfrom the line 32 to the line 34 and, contrariwise, when the valve control lever 30 is shifted to an opposite position, the oil under pressure in the line 34 will be permitted to flow backwardly to the return line 33. a I

Similarly, another chamber a of the control valve 29 is connected by means of flexible oil pressure lines 35, 36, to manually adjustable flow-regulating valves 37, 38, and pressure-relief valves 39, 40, the latter being connected on their discharge sides to each other by a bypass line 41 and in common to a discharge line 42, which is, in turn, connected through a flexible conduit 43 to a T-fitting 44 forming part of the return line 33.

The oil motor 20 is provided with two inlet connections 45, 46, respectively connected through interconnected fittings 47, 47', and 48, 48', to the flow-control valves 37, 38, and pressure-relief valves 39, 40, and by a T-fitting 42- to the discharge line 42, the latter connection serving the purpose of draining off any oil that leaks past the vanes of the fluid motor 20. The connections are best seen in Figure 6. When the control lever 31 is in neutral position, no oil will flow through either of the oil lines 35, 36. However, when the control lever 31 is shifted to one of its alternative positions, oil pressure will be permitted to flow from the main pressure line 32 through the line 35 to turn the oil motor 20 in one direction and the oil returning from the motor 20 will flow through the line 42 and the conduit 43 to the oil return line 33. Contrariwise, when the control lever 31 is shifted to its opposite or alternative position, the flow of the oil is directed through the line 36, and the direction of rotation of the oil motor 20 is correspondingly reversed. As the motor 20 rotates, the shaft 17 will turn and propel the extension ladder section 25 either up or down, as It will, of course, be evident that by changing the direction of rotation of the oil motor 20, the direction of movement of the extension ladder section 25 can be correspondingly changed. The manually adjustable flow-control valves 37,38, and the pressure-relief valves 39, 40, are conventional and readily available elements and are, therefore, not described herein in detail. Devices of this type are commonly used in various different ways in hydraulic systems and the present invention does not particularly relate to the internal construction thereof, but the utilization of aconstant torque oil motor in conjunction with two flow-control valvesand two pressure-relief valves in the particular circuit arrangement herein disclosed is an essential part of the present invention, and, to this end, it should be pointed out that a flow-control valve operates to receive hydraulic fluid on its inlet side at a relatively high pressure, but variable volume, and to pass ,the;hydraulic fluid to its outlet or discharge side at substantially constant volume or flow, but correspondingly variable pressure. The utilization of thistype of device in combination with a constant displacement or rotary type of fiuidmotor of the constant torque type insures that a maximum predetermined amount of volume will pass through the motor.

By'pr'oper adjustment of the relief valves, themaximumtorque of the oil motor20 can be controlled and the Jam ng dd rscct onwillf .come to either end .ofjts stroke and stop smoothly and without damage. Furthermore, the flow-control valves 37, 38, are'inserted in 'a manner that otters unrestricted flow at the exhaust side of the oil motor 20. By this arrangement, the restrictions of flow, and subsequent increase in pressure, are limited to the locality between the pump and the flow-control valves 37, 38. r

The pressure-relief valves 39, 40, are placed between the flow-control valves 37, 38, and the oil motor 20. The by-pass oil from these valves returns throughthe discharge line 42-and thence to the main oil return line 33, as previously stated. The relief-valves 39, 40, operate to control the maximum torque output of the oil motor 20 for either direction of rotation. Torque is governed by the pressure drop across the oil motor 20, and, since the return line 33 is at substantially atmospheric pressure, the inlet pressure becomes the governing factor. There must be suflicient torque developed for extending the ladder section 25 at any angle of elevation, but there must notbe excessive force which would damage the structure as the ladder section 25 reaches either limit of its normal path of movement. By proper adjustment of the relief-valves 39, 40, the oil motor 20 will quickly shift the ladder section 25 to either limit ,of its movement, and when such limit is reached, will stop, and any excessive torque-producing back pressure, which would otherwise build up in the system, is dissipated through one or the other of the pressure-relief valves 39, 40. It, of course, is apparent that one or the other of the pressurerelief valves 39, 40, will be operative, depending upon the direction of rotation of the oil motor 20. The hydraulic system or circuit herein employed is uniquely adapted to permit direct application of power from the oil motor 20 to the shaft 17 without the interposition of speedreduction gearing, and, therefore, makes, shock-free operation possible, and it is possible to obtain the required driving torque without resort to extremely high inlet pressures to the oil motor 20.

It should be understood that changes and modifications in the form, construction, arrangement, and combination of the several parts of the powerdriven aerial extension ladder may be made and substituted for those herein shownand described without departing from the nature and principle of my invention. a a t t 1 Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In an aerial ladder comprising an upright pedestal, a ladder-supporting framework pivotally mounted on the pedestal for rotation about a substantially vertical axis, a main ladder section pivotally mounted on and carried by the framework for rocking movement about an axis transverse to the upright axis, said main ladder section being provided with edgewise aligned spaced pulleys, a second ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluidmotor drivingly connected to one of said pulleys and adapted to have a maximumtorque output for high loads and a torque output which ad- ,justs to the requirements of the load when the maximum a mainladder section pivotally mounted on and carried by the framework for rocking movement aboutan axis transverseto the upright axis, said main ladder' section being provided with edgewise aligned; spaced pulleys, a s eggnd ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluid motor drivingly connected to one of said pulleys and adapted to have a maximum torque output for high loads and a torque output which adjusts to the requirements of the load when the maximum torque is not required, of means for supplying said motor with a fluid having constant volume flow under varying pressures for driving said motor, and a relief valve operatively interposed between the supply means and the motor.

3. In an aerial ladder comprising an upright pedestal, a ladder-supporting framework pivotally mounted on the pedestal for rotation about a substantially vertical axis, a main ladder section pivotally mounted on and carried by the framework for rocking movement about an axis transverse to the upright axis, said main ladder section being provided with edgewise aligned spaced pulleys, a second ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluid-operated motor having a drive shaft coupled to one of said pulleys and a pair of inlet ports and an outlet port whereby when fluid is passed through said motor from one inlet port to the outlet port said drive shaft is caused to rotate in one direction and when fluid is passed through said motor from the other inlet port to the outlet port said drive shaft is caused to rotate in the opposite direction, said motor being adapted to operate at a constant maximum torque under variable speed and being adapted to adjust its torque to the requirements of the load when the maximum torque is not required, of a stationary source of fluid under pressure, selecting means for delivering fluid from said source to either of said inlet ports through a pair of independent feed lines, flow control means interposed in each of said feed lines for passing fluid therethrough at a constant volume rate under varying pressures, and relief means interposed between the flow control means and each of said inlet ports and adapted to by-pass the motor when the extending means has been raised and lowered to its limit, said relief means also being adapted to remove leakage fluid from the motor during operation thereof.

4. In an aerial ladder comprising an upright pedestal, a ladder-supporting framework pivotally mounted on the pedestal for rotation about a substantially vertical axis, a main ladder section pivotally mounted on and carried by the framework for rocking movement about an axis transverse to the upright axis, said main ladder section being provided with edgewise aligned spaced pulleys, a second ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluid-operated motor having a drive shaft coupled to one of said pulleys and a pair of inlet ports and an outlet port whereby when fluid is passed through said motor from one inlet port to the outlet port said drive shaft is caused to rotate in one direction and when fluid is passed through said motor from the other inlet port to the outlet port said drive shaft is caused to rotate in the opposite direction, said motor being adapted to operate at a constant maximum torque under variable speed and being adapted to adjust its torque to the requirements of the load when the maximum torque is not required, of a fluid reservoir, a pump having its intake connected to said reservoir, a directing valve operatively connected to the output of said pump for selectively supplying fluid under pressure from said pump to either of the inlet ports of said motor, flow control means interposed in each of said feed lines for passing fluid therethrough at a constant volume rate under varying pressures, and relief means interposed between the flow control means and each of said inlet ports and adapted to by-pass the motor when the extending means has been raised and lowered to its limit, said relief means also being adapted to remove leakage fluid from the motor during operation thereof.

5. In an aerial ladder comprising an upright pedestal, a ladder-supporting framework pivotally mounted on the pedestal for rotation about a substantially vertical axis, a main ladder section pivotally mounted on and carried by the framework for rocking movement about an axis transverse to the upright axis, said main ladder section being provided with edgewise aligned spaced pulleys, a second ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluid operated motor having a drive shaft coupled to one of said pulleys and a pair of inlet ports and an outlet port whereby when fluid is passed through said motor from one inlet port to the outlet port said drive shaft is caused to rotate in one direction and when fluid is passed through said motor from the other inlet port to the outlet port said drive shaft is caused to rotate in the opposite direction, said motor being adapted to operate at a constant maximum torque under variable speed and being adapted to adjust its torque to the requirements of the load when the maximum torque is not required, of a fluid reservoir adapted to receive the fluid from the relief means, a pump having its intake connected to said reservoir, a directing valve operatively connected to the output of said pump for selectively supplying fluid under pressure from said pump to either of the inlet ports of said motor, flow control means interposed in each of said feed lines for passing fluid therethrough at a constant rate under varying pressures, and relief means interposed between the flow control means and each of said inlet ports and adapted to by-pass the motor when the extending means has been raised and lowered to its limit, said relief means also being adapted to remove leakage fluid from the motor during operation thereof.

6. In an aerial ladder comprising an upright pedestal, a ladder-supporting framework pivotally mounted on the pedestal for rotation about a substantially vertical axis, a main ladder section pivotally mounted on and carried by the framework for rocking movement about an axis transverse to the upright axis, said main ladder section being provided with edgewise aligned spaced pulleys, a second ladder section slidably mounted on the main ladder section for telescopic movement with respect thereto, and an endless driving cable connected to the second ladder section and operatively trained around the pulleys of the main ladder section, the combination with a reversible fluid-operated motor having a drive shaft coupled to one of said pulleys and a pair of inlet ports and an outlet port whereby when fluid is passed through said motor from one inlet port to the outlet port said drive shaft is caused to rotate in one direction and when fluid is passed through said motor from the other inlet port to the outlet port said drive shaft is caused to rotate in the opposite direction, said motor being adapted to operate at a constant maximum torque under variable speed and being adapted to adjust its torque to the requirements of the load when the maximum torque is not required, of a fluid reservoir adapted to receive the fluid from the relief means, a pump having its intake connected to the output of said pump for selectively supplying fluid under pressure from said pump to either of the inlet ports of said motor, flow control means interposed in each of said feed lines for passing fluid therethrough at a constant volume rate under varying pressures, and relief means interposed between the flow control means and each of said inlet ports and adapted to by-pass the motor when the extendmeans has beenjraised and lowered to its lirnit, said relief means; also being. adapted e to, remove leakage fluid from the motor during operation thereof, and to return said leakagefiuid to said reservoir.

.51. The combination of claim 6 wherein the flow control means comprises a pair ,ofiflow-regulating valves adapted to receive fluid under constant pressure at varying volumetric rates, and to forward, fluid at constant sure in the respective feed line is belowa certain predetermined level, and also being adapted to transfer fluid directly from the flow-control means to the reservoir when the pressure in any feed line exceeds said predetermined leveL V 9. The combination of claim 3 wherein all the elements of said combination are specifically adapted to operate with hydraulic fluid. p

10. The combination of claim 6 wherein all the elements of said combination are specifically adapted to operate with hydraulic fluid.

11. In an aerial ladder comprising a main ladder section, a second ladder section slidably mounted on said main ladder section for telescopic movement with respect thereto, and driving means operatively connecting the main ladder section and second ladder section; the combination with a rotary fluid motor operatively connected to said driving means, said motor having a constant maximum torque at variable speed and being adapted below such maximum to adjust its torque to the requirements of the load, said motor having an input line and a discharge line, of a flow-regulating valve in the input line and operable to pass hydraulic fluid to said motor under variable pressure and at a substantially constant rate of flow, a pressure relief valve in said input line, and a bypass line on the discharge side of the relief valve, and connected to the motor-discharge line whereby to permit the oil motor to idle when the second ladder section reaches the end of its stroke.

12. In an aerial ladder comprising a main ladder section, a second ladder section slidably mounted on said main ladder section for telescopic movement with respect gnain laddersection and second ladder sectiongthe combination with a rotary fluid motor operative'lyconnected to saiddriving means, said motor having constant maximum torque at variable speed and being adapted below such maximum to a djust its torq'ueto the requirements of the load, said motor having an input line and a discharge line, of a flow-regulating valve intheinput line and operable to pass hydraulic fluid to said motor under variable pressure and at a substantiallyconstant rate of flow, a pressure relief valve in said input line and interposed between the motor and flow-regulating valve, and a by-pass line on the discharge side of the relief valve and connectedto the motor-discharge line whereby to permit the oil motor to idle when the second ladder section reaches the end of itsstroke.

13. For usei'vvith an aerial'ladder; arotary oil motor having constant maximum torque at variable speed and being adapted below such maximum to adjust its torque to the requirements, of the load, said motor having an input line and a discharge line, a flow-regulating valve in the input line and operable to pass hydraulic fluid under variable pressure and at a substantially constant rate of flow, a pressure relief valve in said input line, and a bypass line on the, discharge side of said relief valve and connected to the motor-discharge line.

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